How the EPA Rates An Electric Car
The EPA (Environmental Protection Agency) is an independent agency of the United States federal government for environmental protection, and its key mission is to protect human health and the environment.
Amongst other things, the EPA is responsible for developing and enforcing regulations written by Congress, offering grants to profit and nonprofit organizations and studying potential environmental issues.
The EPA is also the government body responsible for testing electric cars and rating their energy efficiency – in the specific, their operating range on a charge.
Despite what people might think this process does not take place on the road but instead it occurs in a laboratory where the energy consumption of a vehicle is tested using standard federal law procedures.
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How testing and rating works
A dynamometer, which is essentially a treadmill for cars, is used to test the vehicles. The engine and transmission operate normally, but the car doesn’t move as the wheels are placed on specially designed rollers.
The car is tested with multiple standardized driving schedules to simulate different scenarios, like basic city-like driving patterns (stop-and-go) or highway driving (higher speeds, no stops).
Actual professional drivers drive the cars.
The cars are tested with a full battery, until it’s fully depleted, through a number of city and highway driving cycles.
After this phase, a technician establishes the car energy consumption by dividing the kilowatt-hours of energy needed to recharge the battery by the number of miles driven.
Each car is then assigned an MPGe rating.
MPGe is a miles-per-gallon equivalent measurement created by EPA to help consumers comparing electric vehicles with standard petrol cars.
To give an example, the 2018 most energy efficient electric vehicle was the Hyundai Ioniq Electric with a score of 150 MPGe in city driving and 122 on the highway.
Factor affecting the testing
The nature of this lab-based procedure can, however, effect the results of the tests.
- Tested are conducted only inside a lab at a room temperature: very high and low temperatures can substantially affect the performance of an electric vehicle.
- The testing is performed with only one driver and no cargo loaded: as it’s easy to imagine this is not the only situation where cars are usually driven.
- Driving style: different driving styles can affect the performance range of the vehicle – a ‘sporty’ driving style will drain your battery more quickly
MONRONEY – The EV “fuel economy” sticker
According to federal US law, important information about a vehicle such its energy consumption, pricing etc is gathered by the carmakers in the so-called Monroney sticker which is posted on every new light-duty vehicle sold in the U.S.
In case of electric cars, the sticker shows info such MPGe estimates for city, highway and combined city/highway driving.
The sticker also details how many kilowatt-hours of electricity are needed by the vehicle to run 100 miles (kWh/100 mi), the range of the car on a charge, and the time that it takes to recharge the batteries using a 240-volt (Level 2) charger.
Interestingly the sticker will also show a comparison with other models in vehicle’s class, the average annual cost to keep your car running (based on 15,000 miles per year) and will compare this figure over a five-year period against the average vehicle of the category.